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Increasing Coal Mine 

Efficiency 


By 

CHARLES E. STUART 

United States Fuel Administration 
Washington, D. C. 





Reprinted from 

COAL AGE 




























T N %of 






















», #<r ->• 

MOV 13 1911 














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V 
















Increasing Coal Mine Efficiency—1 

By CHARLES E. STUART 

United States Fuel Administration, Washington, D. C. 


SYNOPSIS — The first of a series of articles 
upon the subject of mine efficiency. Many oper¬ 
ators and “practical” coal men do not yet realize 
that the power generation and distribution sys¬ 
tem of the fair-sized mine offers problems more 
complicated and intricate than exist in the ordi¬ 
nary town of 25,000 inhabitants. 

Introduction 

I N ANY present-day consideration of coal-mine oper¬ 
ation having in view increased coal production and 
operating efficiency, certain war factors must con¬ 
stantly be borne in mind. No study of the subject can 
be properly made without due al¬ 
lowance for existing war condi¬ 
tions, such as decreasing availabil¬ 
ity of required machinery; in¬ 
creased delay in obtaining factory 
repairs or repair parts; increasing 
load on central stations already 
frequently overtaxed; and decreas¬ 
ing man power incident to the re¬ 
quirements of the army and as a 
result of the tempting offers of 
other classes of war industry. 

There is urgent demand for 
every pound of steel that can be 
produced. This is needed for the 
construction of ships, and for the 
manufacture of shells and other 
war material. Furthermore, the 
man with the skill to turn the axle 

of a mine locomotive can likewise turn an urgently 
needed shell; in a word, we are short of both skilled 
labor and raw material for imperative war requirements. 
Nevertheless, and in spite of these facts as well as 
because of them, we must increase the production of 
coal. 

This series of articles will not be technical. An oper¬ 
ator who regards himself as qualified to purchase a fan 
motor need not hesitate to study it because of the in¬ 
troduction of curves and other descriptive technical 
data. The operator capable of specifying and purchas¬ 
ing such a motor will recognize the information as ele¬ 
mentary. He will also agree that the facts presented 
are logical, and they may perhaps recall considerations 
to which he has at odd times given some casual thought, 
or difficulties which he has definitely attempted to solve. 

The fact that electrical and mechanical engineering 
skill has become as important a factor in the efficient 
management of mining properties as civil engineering 
ability, is today appreciated only by some of the larger 
and better organized operating companies. 

Fig. 1 summarizes the results of a number of com¬ 
parative analyses. The physical handicaps of the prop¬ 
erties have a bearing on the extremes indicated, but 


these considerations have, relatively speaking, only a 
small influence. The following report of power con¬ 
sumed and tonnage output is illustrative: 


I5-Min. Demand, Kw. 

Consumption, 

Tonnage 

Kw -Hr. 

Operation No. 1 

Kw.-Hr. 

Output 

per Ton 

June 518 

90,700 

35,000 

2.7 

July 547 

101,600 

36,400 

2.8 

Operation No. 2 

June 374 

112,100 

60,599 

19 

July 412 

123,400 

60,946 

2.0 


In different mines— 

The cost of power per ton 
varies 1,000% 

The cost and time for gathering 
a car of coal varies 600% 

The cost of cutting varies 500% 

Repair costs vary 800% 


FIG. 


Mine No. 1 consumes 40 per cent, more power and has 
30 per cent, higher power demand. There is some dif¬ 
ference in the operating conditions, but nothing that 
would cause such a wide variation of output to demand 
as that cited above. 

The average town of 25,000 population contains a 
pumping plant, which takes its water from a single 

source by a single lift. The mu¬ 
nicipality contains a well-regu¬ 
lated trolley system. There may 
be several factories containing 
more or less complicated systems 
of electrical drive, and in each and 
every instance there is maintained 
a well-organized engineering force 
headed by a capable electrical or 
mechanical engineer, or an engi¬ 
neer manager. 

The mine with a capacity of 
1000 tons a day contains a gener¬ 
ating or converting plant, the load 
upon which corresponds both in 
diversity and complexity to the 
combined requirements enumer¬ 
ated in the case of the town of 
25,000. The pumping system of 
the mine is invariably more complicated. If the miner 
is not properly served by the haulage system, he becomes 
idle through a greater or less period of time. 

The subject of mine ventilation considered in rela¬ 
tion to power demand and consumption is in itself an 
art to which the town offers no parallel. Extremely 
few factories, for instance, contain motor drives whose 
needs in the way of skilled attention compare with the 
requirements of a tipple designed to prepare coal prop¬ 
erly for coking and for the market. The lighting re¬ 
quirements of the average mine camp are identical 
to those of the small town, provided the miners’ homes 
are to receive reasonably good service and the mine 
itself is to be properly lighted. 

In many instances a mine operator does not appreci¬ 
ate the complexity or possible efficiency of his expensive 
equipment, and is entirely satisfied with an electrician 
who can keep things going. Frequently, such electri¬ 
cians are capable of serious efficiency work and would 
gladly undertake it if requested or encouraged to do so 
and furnished with the necessary assistance. Such an 
attitude on the mine operator’s part is distinctly short¬ 
sighted and results in loss of greatly needed coal pro¬ 
duction, both to the mining company and to the country. 


COMPARATIVE ANALYSES 
SUMMARIZED 


[ 3 ] 





There is another phase of equal importance to the 
operator from a personal viewpoint—namely, the rela¬ 
tionship of investigation and improvement recommended 
herein to cost and profit. Every recommendation made, 
if carried out, will save money; or, conversely, will make 
money for the mine operator. It should be remembered 
also that no suggestion is made in this series of articles 
whose value has not been fully demonstrated in practice. 
These suggestions are not impractical and will only 


ments tending to delay him. It is the rule to blame 
the miner for a small day’s production, but we rarely 
hear of the superintendent or foreman taking unto him¬ 
self criticism for failure to keep the miner properly sup¬ 
plied with cars. 

The showing in Fig. 2 is by no means a poor one, or 
below the average. On the contrary, the group of mines 
where the observations were made are supposed to be 
among the most efficiently operated in the country; and 



FIG. 2. COMPARATIVE PERFORMANCE OF MINERS IN 

THREE MINES 


appear so to the superintendent or owner who is unable 
to grasp their significance, or who is unwilling to give 
the small amount of time necessary to digest the recom¬ 
mendations here made and put forth the subsequent 
effort that may be requisite in order to carry them out. 

To repeat, I am endeavoring to bring to bear a few 
simple analyses to show that the mine operator with the 
help at hand is in position to go a great deal farther 
today than he is now going to meet the demand for con¬ 
servation in its broad economic sense. 

None of the considerations and conditions enumerated 
in the foregoing should be overlooked in considering the 
following factors in mine operation, which will be 
covered in this series of articles: (I) A comparative 
analysis of a miner’s working day. (II) An analysis 
of the performance of mine locomotives. (Ill) An 
analysis of the performance of cutting machines. (IV) 
The power demand and consumption of mine fans. (V) 
An analysis of power demand and consumption of mines 
in relationship to capacity and production. (VI) An 
analysis of mine power conditions in relationship to pro¬ 
duction. (VII) A consideration of track conditions in 
relationship to production. (VIII) The condition of the 
generating plant. (IX) The relative output of electri¬ 
fied vs. unelectrified mines. (X), Considerations in 
the case of a shortage of central station capacity. (XI) 
A coal mine efficiently electrified using purchased power. 


TABLE I. AVERAGE PERFORMANCE OF EQUIPMENT AND MINERS 


Hoist: Minutes PerCent. Gatherers: Minutes PerCent. 


Hoisting cars. 

231 

51.2 

Hauling. 

286 

49.7 

Hoisting supplies.... 

125 

22.3 

Running light. 

81 

14 1 

Waiting for loads.... 

123 

22 0 

Waiting on loads.. .. 

89 

15.5 

Wrecks. 

60 

10 8 

Waiting on empties.. 

75 

13.0 

Idle. 

21 

3.7 

Waiting on drivers. . 






Wrecks. 

28 

4.9 

Total. 

560 

100.0 

Idle. 

16 

2.8 

Haulage Motors: 




575 

100.0 

Hauling. 

Running light. 

284 

39 

49.3 

6.8 

Miners—Average of 6 Men 


Waiting on loads.. . . 

73 

12 6 

Loading. 

217 

41 9 

Waiting on empties.. 

10 

2.0 

Picking. 

141 

27.2 

Waiting on motors. . 



Idle. 

53 

10 2 

Wrecks. 

164 

28.2 

Waiting on cars. 

60 

11.5 

Supplies. 

6 

1 1 

Timbering. 

25 

4 8 




T ran3portation. 

23 

4.4 

Total. 

576 

100.0 







Total. 

519 

100 0 


furthermore, their output of coal per miner is a record 
output. Table I gives several average performances of 
equipment and miners. 

Fig. 4 is a graphic analysis of daily performance 
showing how the summary in Fig. 2 and the compara¬ 
tive analysis in the table are obtained. We are par¬ 
ticularly concerned with those elements of delay which 
bring about the “wait on cars.” Such delays may be 
classified under the heads of “avoidable” and “unavoid¬ 
able.” Unavoidable delays are those such as occur in 
any system of transportation. For example, there will 
be delays incident to transfer of cars from one locomo- 


y'lQO % Efficiency under conditions that might have prevailed 


Complete circle 
represents iOO/t'—yf.^ 
efficiency -300 ' 

cars hauled per 
day 



The above in its relationship is practically characteristic of mine haulage 

in general. 

Similar tests several weeks later after power and other conditions had 
been improved, indicated a 100 °/o increase in productive effort and 
proportional decrease in equipment neeaed for word produced, power. 

consumption and other incidental costs. 

This chart represents one step in a test carried from boiler to 
face of coat 

A • Possible work under prevailing conditions. 

B * Possible work under conditions which might have prevailed 


I—Comparative Analysis of a Miner’s 
Working Day 

Fig. 2 shows the comparative performance of miners 
in three different mines, two of which are electrified. 
To arrive at these summaries, a careful analysis was 
made not only of the actual employment of time by the 
miner, but also in order to locate and isolate all ele¬ 


FIG. 3. GRAPHIC ANALYSIS OF DAILY PERFORMANCE 
OF LOCOMOTIVES 

tive to another. Wrecks may occasionally be classified 
as unavoidable. 

In a general way, avoidable delays as here considered 
are such as are occasioned by a section of the haulage 
system being congested or inadequate for the work. The 
chief causes which are responsible for the element of 


[ 4 ] 













































































































TIME 


6 !2 Z4 36 48 7 !2 24 36 48 8 /2 24 36 48 9 !Z 24 36 48 !0 /Z Z4 36 48 // /Z 36 48 /2 !Z 24 56 48 / !Z Z4 36 48 2 /Z 24 36 48 3 


a 

5 


( 80 
40 

m/r/NO FOR LOADS 
WRECKS 
TRACK BLOCKED 

„£ 1 40 

oj CARS HAULED 1 

e m LO 

O C \Q 

o ° • Rum/HG LIGHT 
s c WAITING tor other holors 
§•£ , , LOADS 

, . EMPTIES 

_ SHIFTIHG - WRECKS--FTC. 
N£ \*0 

6% I JO 

* $ CARS HAULED < ZO 

§1 Vo 

PCIMN/HG LIGHT 
Z kWA/T/MG FOR OCHER MOTORS 
, , LOADS 

„ ?. Smft/h'g ~wr$cksc fit. 
el. 0 - 

go CARS HAULED V/o 

£5 RUHHING LIGHT 
B i MUTING FOR OTHER MOTORS 
15 & v LOADS 

g ? I . EMPTIES 
x j SHIFTING-WRECKS-FTC. 



PICKING 

TIMBERING,TRACK 
2 IDLE 

p WAITING FDPCARS 
£ PICKING 

T/MBER/Np, TRACK 



FIG. 4. COMPOSITE RECORD OF PERFORMANCE OF LOCOMOTIVES AND MINERS 


time loss shown in Fig. 2, and which may be classified as 
avoidable, are as follows: (1) Handling supplies; (2) 
sanding motors at other points than where stops are 
regularly made; (3) insufficient capacity of loaded and 
empty partings; (4) poor signal system; (5) insufficient 
number of cars; (6) wrecks; (7) locomotive trouble due 
to lack of inspection; (8) delay due to failure to place 
car ready for miner on his arrival; (9) indifference of 
motormen; (10) bad management. 

II—Analysis of Mine Locomotive Performance 

The converse of the analysis of a miner’s working 
time is indicated in Fig. 3. Here we have the composite 
record of the average performance of a number of 
gathering locomotives as taken in different mines. Prac¬ 


tically speaking, the record is characteristic of mine 
haulage. One hour and 20 minutes out of the day is 
shown waiting on miners and 2 hours 2 minutes are 
spent in idleness or loafing. 

I have observed many tests of mine locomotives with 
the object of developing such comparisons as the fore¬ 
going. I have never observed a single test—that is to 
say, a trial carried through the period of a day—that 
failed to show serious elements of time lost that could 
not be classed under the head of avoidable. 

The elements of delay derived in Section I are also 
the basis of time wastage in the locomotive movement. 
In fact, as is readily appreciated, a delay which would 
prevent the prompt serving of a miner with cars would 
similarly as a rule reduce the efficiency of operation of 


CARS'-- 

CARRYING SUPPLIES FTC. 
RUNNING L/6NT 
WAITING ON SAND 
FE^!RS WOrHERMOTORS 
ON SIGNALS 

CARS-. 

CARRYING SUPPLIES ETC. 
RUNNING UGHT 


Z ON SIGNALS 

CARS-. 

CARRYING RAILS ETC. 
RUNNING LIGHT 

m T" go r e %'moTors 

REPAIRS 

WRECKS 

.(« 

GARRy/NS RAILS ETC. ' 

REPAIRS 

WRECKS 

%& NEMPT,ES 

CARS 

CARRY!N6 RAILS ETC. 
RUNNING LIGHT 
WAITING ON MINERS 

- OTHER MOTORS 


WAITING ON EMPTIES . ( pzTZ: 

CARS.fV 

CARRYING RAILS ETC. ' IA 

RUNNING L !QH T K 1 -— 

WAITING ON MINERS 

» " OTHER MOTORS 

WAmffS ON EMPTIES 
LOAFING 

CARS.- 

CARRYING RAILS ETC. 

RUNNINGUGHT 

WAITING ON MINERS _ 

" » OTHER MOTORS 

’wrecks 

'loAFnfe 0N EMPTIES 

CARS- 

CARRYING RAILS ETC. 

RUNNING UGHT 
WAITING C .. 


VYRECKS 
WAIT-" 


WAITING. ON EMPTIES 
.LOAFING 



NO.l MAIN LINE MOTOR yj£D 9-30-19/4 


WALTER CECIL.MOTORMAN 
FRANK BARTON. BRAKE MAN 
HAULED OUT 57S LOADS, 566 EMPTIES IN 
TIME HAULING CARS AND SUPPLIES 360 MIN. 
” NOT HAULING £70 '* 


NO. 1 MAIN LINE MOTOR ThURS. IO-I-I9I4 

WALTER CECIL.MOTORMAN 
FRANK BARTON, BRA NEMAN 
HAULED OUT 173 LOADS, DIO EMPTIES IN 
TIME HAULING CARS AND SUPPLIES 390 M/N. 
>• NOT HAUUNG 540 •* 


METH0D-CHAN6IN6 ON MINERS. 

YiO.Z GATHERING MOTOR FRIDAY 10-5-19/4 
FRANK KELLY, BPAKEMAN 
MACK HOLBROOK. MO TOR MAN 
RUNNING FROM !0 LEFT FARTING TO JO LEFT ENTRY 
TIME HAULING CARS ANDSUPPUES 330 M/N. 

■» NOT HAULING 300 •» 

LOADS 53 EMPTIES 19 
METHOD-CHANGING ON MINERS. 

NO.'S GATHERING MOTOR MONDAYI0-5-I9M 

E.S.DIHART, MOTORMAN 
SAM DODD, BRAKEMAN 

RUNNING FROM 10 LEFT P, >RTIN& TV JO LEFT ENTRY 
TIME HAULING CARS AND SUPPUES 460 MIN. 

» NOT HAULING 175 « 

LOADS 45 EMPTIES 34 

METHOD-CHANGING ON MINERS, 

ALSO PULLING AND PLACING 

NO.5 GATHERING MOTOR TUES, IO-G-19/4 

EARL PR/VETT. MOTORMAN 
WILLIE FIELDS. BRAKEMAN 

RUNNING FROMSLEET PARTING 7069:9LEFT ENTRIES 
TIME HAUUNG CARS ANDSUPPUES 403 M/N. 

” NOTHAUL/NG 527 » 

LOADS 47 EMPTIES 49 
METH0D-CHAN61N6 ON MINERS. 

ALSO PULLING AND PLACING 
NO. 5 GATHERING MOTOR WED. 10-7-1914 
EARL FR/YETT MOTORMAN 
WILLIE FIELDS. BRAKEMAN 
RUNNIN6 FROM Q LEFT FARTING TV 6 EC 9 ENTRIES 
TIME HAUUNG CAPS AND SUPPLIES 450 M/N. 

» NOT HAULING JOO » 

LOADS 47 EMPTIES 4S 
METHOD-PULLING AND PLACING 
N0.6 GATHERING MOTOR THUPS. 10-&-T9M 
GEO-DONLEY. MOTORMAN 
TONY SMITH, BRAKEMAN \ 

RUNNING FROM 10 LEFT PARTING TO H L.6U3R. ENTRIES 
TIME HAUUNG CARS AND SUPPLIES 4!5 M/N. 

” NOT HAULING 2/6 n 

LOADS 45 EMPTIES 34 
METHOD-PULLING AND PLACING 
N0.6 GATHERING MOTOR FRIDAY 10-9-19/4 
6EO. DONLEY. MOTORMAN 


RIE3 


LOADS 4! EMPTIES 33 


o Porting x Loaded Care • Empty Cars ©Tipple 

FIG 5 CHART OF PERFORMANCE OF SEVERAL LOCOMOTIVES IN THE SAME MINE 

[5] 



































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































the haulage system. There is also the factor of manage¬ 
ment which adjusts the movement of locomotive and 
cars to the requirements of the miner. Failure to prop¬ 
erly make such adjustment will necessitate either the 
locomotive waiting on the miner or the miner waiting 
on the locomotive. 

Fig. 5 is the chart of one day’s work of several loco¬ 
motives in the same mine. Such a chart can be easily 
developed for the entire haulage system so as to isolate 
the elements of avoidable time wastage. If such an 
analysis is properly prepared for and accurately con¬ 
ducted, it will usually be found that locomotives which 
were thought necessary can be done without. It will 
often be discovered that a mine overequipped from a 
haulage standpoint. I have observed increases of more 
than 100 per cent, in productive effort following care¬ 
fully conducted examinations of this character. 

A locomotive is usually regarded as necessarily sub¬ 
ject to frequent breakdowns incident to controller 
trouble, bearing trouble and armature burnouts. When 
these troubles are too frequent, the manufacturer is 
blamed. Nevertheless the manufacturers who supply a 
considerable proportion of mine locomotives in use like¬ 
wise supply approximately 100 per cent, of street-car 
motors, which are in nearly all respects similar in de¬ 
sign to the mine motor. 

A street-car motor is supposed to last about five years 
before it becomes necessary to rewind it. During that 
period it is expected to do 200,000 car-miles. Provided 
a mine motor is of proper capacity for its work, there 
is no reason why its lasting qualities measured in pe¬ 
riod of time should not be equal to that of the street¬ 
car motor. The mileage, of course, will not compare. 

Why Motor Trouble on Street Cars Is Rare 

We all know how rare it is for a street car to stop 
on account of motor trouble. In spite of the number of 
cars in operation in a great city, a tie-up on account of 
trouble with a motor is a rare occurrence. The reason 
is that the rated voltage is supplied at all times and 
there is daily inspection. 

I visited a number of mines in Germany some years 
ago in order to observe the mine machinery in use. On 
commenting upon a daily delay sheet that was kept, and 
the absurdly low repair cost as well as the small amount 
of time used in effecting repairs, I was advised that 
this was due to the daily inspection which all machinery 
underwent. The rule of the railways should be fol¬ 
lowed and the mine locomotive should be subjected to 
daily inspection by a competent man. The following 


parts should be examined with particular care dailj r : 
First, controller segments should be filed and greased 
with vaseline. Second, every bearing should be oiled 
and packed. Third, brushes and commutators should 
be watched carefully. Fourth, the distance between 
armature and pole pieces should be gaged weekly. If 
these parts are kept under observation in the manner 
suggested, locomotive troubles will become nearly neg¬ 
ligible and actual breakdown in the mine will become 
practically unknown. 

A suggestion in connection with the operation of the 
haulage system, which on its face may appear radical, 
is what might be termed in a dispatcher system, corre¬ 
sponding to the system in use on all electric railways as 
well as railroads. We have reference to a man whose 
duty it would be to observe and systematize the move¬ 
ment of equipment in the mine and who would keep 
check on delays of the character recorded in Sections I 
and II. He should maintain a system of checks and 
charts which would throughout the day’s work inform 
him as to the condition of the rooms and the relative 
location of cars, locomotives and machines. This man, 
if of the proper training, could also carry out or direct 
the tests and investigations recommended in the several 
sections. We have observed the partial adoption of this 
system in one or two cases, and the results have been 
gratifying. There is no question but that if the mines 
of the country would adopt such a system, and if com¬ 
petent men could be utilized for the work, exceedingly 
valuable results would follow in relationship both to cost 
and production. 

There should be at the disposal of the mine officials 
or a dispatcher a comprehensive mine telephone system. 
A good telephone system is as necessary to efficient mine 
operation as it is to a trolley system or a railroad. It 
will increase production and reduce the cost. It is the 
opinion of coal properties in which telephone systems 
have been installed that these systems rapidly become 
essential to efficient handling of the mines. 

Mines which have been equipped with telephone serv¬ 
ice, and these systems properly used, have shown marked 
increase in production through scheduling of main-line 
locomotives. The telephone tends to reduce the number 
of wrecks. It enables the mine foremen to keep in touch 
with each locomotive, making it possible for them to 
direct and control movements to advantage. We believe 
from observation of mines that have installed telephone 
systems that it is one of the best investments a mine 
operator can make. When properly installed, the main¬ 
tenance is a small item. 


[ 6 ] 




Increasing Coal Mine Efficiency—II 

By CHARLES E. STUART 

United States Fuel Administration, Washington, D. C. 


SYNOPSIS — In a general way, cutting ma¬ 
chines are quite similar in their power require¬ 
ments to locomotives. The proper means and 
speeds for driving mine fans as well as properly 
maintained air courses sometimes result in enor¬ 
mous economies in power. Fluctuating loads on 
the mine generating station or substation should 
be avoided as far as possible. This is often 
much more nearly possible than many operators 
believe. 


Ill—An Analysis of Performance of Cutting 

Machines 

T HE general considerations which govern the 
utilization of a mine locomotive, in order that 
maximum efficiency may be obtained, apply in a 
similar manner to the cutting machine. There are, 
broadly speaking, the same elements of avoidable and 
unavoidable loss of time. There is also the need of 
so developing the mine that the cutting machine can 
be used at its rated capacity. Bad power conditions 
and inefficient handling are factors to the same degree, 
as in the case of the locomotive, and there is the 
same loss in productive effort. 

The ideal method of working a cutting machine is 
to give one machine a section containing sufficient places 
to enable the machine runners to cut each place every 
other day, letting the loaders clean up in the same man¬ 
ner. If this be done, the machine runners usually 
stay on one entry and go into the rooms consecutively 
instead of running all over the mine to cut a place here 


and another there, thus consuming more time in tram¬ 
ming than in cutting. 

In some of the large mines in Pennsylvania and 
Illinois these ideal cutting conditions are very nearly 
attained. In one case with which I am familiar, the 


70 


60 


50 


L 

<+- 3 
° O 

w E 

TS i 
C4- 

S O 

ll 

•C O 
h- 

* 


40 


30 


20 


10 













































































































































































































































































































































































































































: 
















































































































































































































H 

=, 



















































































































































(H<(L<333luUOld<U < !t<33 3uuOU 

-v i. V rf V t rv ^ ii 


mozQTiLZ<j:’n<i/)ozo-)ii.E<i:TT<«ozo 

1912 


1913 


1914 


FIG. 6. 


RESULT OF IMPROVEMENTS IN VENTILATION ON 
PTtWF'/R rnMSTTMKn 


depth of the undercut has been proportioned to the 
width of the room and the height of the coal, in order 
to give just enough coal for the loaders to clean up in 
one or two full days. This enables the maximum effort 
to be put forth by the loader and machine runner. 





i. 


Date 

I 

Sept. 

3 

4 
6 
8 

11 

12 

13 

14 

15 

17 

18 

19 

20 
21 

23 

24 

25 

26 

27 

28 
29 

Oct. 

1 

2 

3 

4 

5 

6 
8 
9 

10 

II 

31 


TABLE II. RECORD TAKEN THROUGH A PERIOD OF 31 DAYS, USING A SULLIVAN SHORTWALL CONTINUOUS CUTTER 

September 3 to October 12, 1917 


Total 


Width, 

Head¬ 

Width 

Narrow 

Width 

Places 

Rooms 

Ft. 

ings 

Ft. 

Places 

Ft. 

2 

3 

4 

5 

6 

7 

8 

5 



3 

14 

2 

14 

5 

"2 

24 

2 

14 

1 

14 

9 

2 

24 

3 

14 

4 

14 

2 

2 

12 


. . 


.. 

9 

2 

24 

5 

24 

2 

14 

9 

3 

28 

4 

14 

2 

14 

12 

6 

24 

5 

14 

1 

14 

12 

7 

25.6 

4 

14 

1 

14 

11 

6 

24 

3 

14 

2 

35 

to 

10 

25 




.. 

8 

A 

31.5 

4 

U 


.. 

9 

6 

26.3 

3 

14 


.. 

5 

4 

24 

1 

14 


.. 

15 

8 

24 

7 

14 


.. 

9 

8 

24 

1 

14 


.. 

10 

7 

24 

3 

14 


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12 

11 

31.5 

1 

14 


. . 

14 

4 

24 

5 

14 

5 

20.8 

9 

7 

22.5 

2 

14 


.. 

6 

2 

29 

3 

14 

' i 

16 

13 

10 

24 

1 

14 

2 

14 

19 

13 

24 



6 

14 

10 

7 

24 

"2 

U 

1 

14 

18 

11 

24 

7 

14 

1 

14 

7 

8 

24 

1 

14 

1 

16 

12 

8 

24 

2 

14 

2 

14 

5 

3 

24 

2 

14 



21 

9 

24 

11 

14 

1 

14 

13 

9 

15.8 

2 

14 

2 

14 

13 

6 

24 

4 

14 

3 

14 

5 

3 

24 

2 

14 



317 

184 

24.2 

93 

14.3 

40 

15.6 


Total Average Total Time Waiting Actual Time 

Face, Cut, Hours for Places, Hours per 

Ft. Depth, In. Worked Etc., Hr. & Min. Work Place, Min. 


9 

10 

11 

12 

13 

14 

70 

84 

10:00 

6:40 

3:20 

40.0 

90 

82 

10:00 

6:20 

3:40 

44.0 

146 

81.2 

10:45 

6:10 

5:35 

37.2 

24 

83 

4:15 

3:30 

0:45 

22. 1 

196 

85 

3:45 

1:05 

4:40 

31.1 

168 

84 

6:45 

1:45 

5:00 

33.3 

228 

80 

8:00 

1:60 

6:10 

30.1 

250 

84 

10:00 

3:50 

6:10 

30.1 

266 

84 

6:30 

1:00 

5:30 

30.0 

250 

83 

6:20 

1:05 

5:15 

31.0 

182 

81 

8:00 

3:00 

5:00 

37.4 

200 

82.2 

10:30 

5:30 

5:00 

33.3 

110 

84 

8:00 

0:30 

2:30 

30.0 

290 

84 

7:45 

0:45 

7:00 

28.0 

206 

85 

5:45 

0:45 

5:00 

33.3 

210 

83 

5:00 

1:00 

4:00 

24.0 

360 

83 

8:00 

1:05 

6:55 

34.7 

270 

81 

7:30 

1:00 

6:30 

27.12 

186 

86 

10:50 

5:35 

5:15 

35.0 

116 

80 

10:00 

7:35 

2:25 

24.1 

282 

84 

6:30 

0:45 

5:45 

26.7 

395 

83 

9:00 

1:05 

7:35 

• 25.0 

207 

82 

7:00 

2:30 

4:30 

25.0 

376 

84 

9:30 

1:10 

8:20 

27.14 

150 

84 

3:45 

0:40 

3:05 

35.0 

248 

81 

6:35 

0:55 

5:40 

28.4 

100 

86 

4:30 

1:30 

3:00 

36.0 

284 

84 

10:00 

1:25 

8:35 

24.11 

198 

83 

7:30 

0:35 

6:35 

30.5 

242 

85 

8:00 

1:45 

6:15 

28.11 

100 

84 

4:00 

1:30 

2:30 

30.0 

6,391 

83.26 

231:00 

73:10 

157.50 

29 87 Min 


Height 

Coal, Ft. 
15 


P 

5i 
5* 
5 h 

?! 

9 

51 

5 

51 

5 

5 

5 

5 

5 

5 

5 

5 


to 6 


to 6 
to 6 


5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 
5 to 6 


66 in. 


[ 7 ] 








































































































Table II shows a record taken through a period of 
31 days, using the Sullivan shortwall continuous cutter. 
During this time 317 places were cut, or an average 
of 10.22 places per day. Column 12, headed “Time Lost 
Waiting for Places,” shows that 73 hours 10 minutes 
were lost. The runner’s report shows that probably 
75 per cent, of this delay could have been avoided. 



FIG. 7. POWER CONSUMPTION OF A MINE FAN 



1912 . 1913 1914 1915 

FIG. 8. POWER CONSUMPTION OF A MINE FAN, SHOWING 
RESULT OF VENTILATION IMPROVEMENTS 


These delays were designated as arising from such 
causes as “blocked by motor,” “no more places cleaned 
up,” “off the track,” etc. Since the average time con¬ 
sumed in cutting a place was a little less than 30 
minutes, it is probable that 100 additional places could 
have been cut if these delays had not occurred, making 
a total of 417 places, or an average of about 13 places 
per day. The average noted in Table II is above the 


usual. There are cases where runners have cut from 
17 to 22 places in 10 hours, these being, however, record 
runs. 

Table III represents tests of power consumption of 
Sullivan room-and-pillar machines, with a 6-ft. 6-in. and 
10-ft. 4-in. cutter-bars. It also gives the comparative 
economies of machines. There is no information con¬ 
tained in these tables which would not be of interest 
and value as determined at every property using a cut¬ 
ting machine. These tests and supplementary observa¬ 
tions develop the following facts: The first cost of the 
machines is practically the same. Repairs on the longer 
bar machines are less than those on the shorter ma¬ 
chines; they are heavier throughout and have fewer 
parts relatively. Experienced men can cut as many 



places with the long bar machines as with the short bar 
machines if voltage is maintained. Loaders after the 
long bar machines use less powder per ton of coal, as 
the same total amount of powder is used per place. 

IV—Power Demand and Consumption 
of Mine Fans 

Figs. 6, 7 and 8 show the results of alterations made 
with the object of reducing power consumption and 
power demand of mine fans. These alterations were 
preceded by investigations and tests which developed 
the following facts: (1) The fans were handling an 
amount of air in excess of the requirements of the 
mine; (2) large proportions of this air failed to reach 
the working faces, due to leakage, defective stoppings, 
brattices and similar reasons; (3) the air pressure, as 
shown by the water gage, was unduly high, owing to 
the air current being carried in too few splits. 

These conditions were corrected by carrying to the 
faces the full amount of air required for good ventila¬ 
tion and by reducing the speed of the air current. 
Stoppings were repaired, and stone was substituted for 
timber in their construction. The speed of the air 


[ 8 ] 




























































































































































































































































































AND 10 FT. 4IN. CUTTER-BARS AND COMPARATIVE ECONOMY OF MACHINES 



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[ 9 ] 


current was reduced by: (a) Institution 
of added splits; (b) cleaning up falls of 
slate in the courses and tunnels; (c) by 
the use of additional air courses where 
possible. 

The fans are now run at the speed re¬ 
quired to obtain the quantity of air 
needed under corrected conditions. At 
night, on Sundays and holidays, half the 
amount of air is handled. In order to 
give the full amount of air for the re¬ 
maining periods, two-speed motors were 
installed. In one case a change was made 
from steam to electric drive. Records 
show that while the steam drive was in 
use, the power consumption amounted 
to the equivalent of 4£ kw.-hr. for every 
ton of coal mined. A constant-speed 
motor, when installed, cut the consump¬ 
tion of power for each ton of coal to 2£ 
kw.-hr., making a 70 per cent, saving by 
installing this one-speed motor. After 
about four months’ service, a two-speed 
motor was installed and the fan was run 
at full speed during the operative period 
of the day, and at half speed at other 
times. The amount of power for each 
ton of coal then dropped to 6 kw.-hr., 
securing a 310 per cent, saving over the 
one-speed motor and a 600 per cent, sav¬ 
ing over the steam drive. 

I might emphasize that these data were 
compiled at a property which first used 
power manufactured at its own central 
station. Later it purchased power. The 
cost of these and other elaborate investi¬ 
gations, the results of which have made 
this property famous throughout the 
country for its efficient methods, repre¬ 
sents a negligible fraction of the econo¬ 
mies produced. 

Figs. 9 and 10 show tests made on 
engine-driven mine fans in the Poca¬ 
hontas coal fields. There is developed 
together with other information the 
horsepower required at different speeds 
and for different air volumes. These 
curves should be carefully considered in 
conjunction with Figs. 6, 7 and 8. The 
latter, as previously stated, show what 
may be done by proper investigation and 
adjustment. 

V—Analysis of Power Demand and 

Consumption in Relationship to 
Capacity and Production 

The demand on the generating plant 
of a coal mine or on the substation in 
cases where power is purchased is of a 
sharply fluctuating character. Fig. 11 
shows the reading of a graphic meter 
taken at a 200-kw. substation. The ex¬ 
treme peaks are the result of short bad 
grades. The mine locomotive, when en¬ 
countering these grades, momentarily 


t 


































































































































































Fan, \A' Jeffery 
Exhausting 

Engine, 16" 

Chandler 
and Taylor 


ff5AD/W65 


HP 

IN 

AIR 

COMB. 

Err. 

% 

SPEED- 

P.PM. 

water 

GAOL 

cu. plain 

PER MIN 

imp 

<60 

05 

71,500 

12.8 

5.6 

0.44 

60 

09 

104,000 

£2.8 

14.7 

0.65 

90 

1.2 

'117.500 

26.8 

T9.3 

‘0.67 

100 

1.4 

'132,500 

36.8 

\G\ 

in 

*0.71 

104 

1.5 

137.000 

45.0 

324 

0.72 

“Estimated from Curve 



Normal Operation, 

Day-IOHrs. at 
95 R.PH. 

Night and Hoi i days- 
6tfrs. at 65R.RM. 



FIG. 10. CURVES OF A STEAM-DRIVEN MINE FAN 



3 Min. Peak t40 Kw. 

5 ’• ’• ZZZ ” 

15 ” ” 164 » 

Max.M'Tary Peak 330Kw. 


3 Min, Peak 190 Kw. 

5 * M 192 »» 

15 *• v w 172 ” 

Max. M’Tary Peak 226 Kw. 


FIG. 11. DEMAND CURVES ON A 200-KW. PLANT 



loads up the station. Few mines are above criticism in 
this respect. With a large percentage of mines the load 
on the generating or converting station is largely com¬ 
posed of more or less avoidable demands. 

Moreover, to an extent that is rarely appreciated, 
such conditions create a “bottle neck” to the entire 
haulage system. Thus a 10-ton mine locomotive on 



50 £50 


40 in £00 
0 
t- 
0 


-1- CL 

530 E 150 

i * 

— <f> 

20 ^ 100 
> 


£.£0 £.Z1 £.££ £.23 Z.£4 £.£5 £.£6 £.£7 Z2& 

Time 

FIG. 13. POWER CONSUMED BY AN 80-HP. LOCOMOTIVE, 
PULLING 20 EMPTIES 



FIG. 14. POWER CONSUMED BY AN 80-HP. HOIST, 
PULLING 12 LOADED CARS 



Time 

FIG. 15. POWER DEMAND OF TYPE B LOCOMOTIVE OF 
80-HP., HAULING 6 LOADED CARS 


level track should haul 31 loaded cars of 4 tons each. 
The same locomotive on a 6 per cent, grade will haul 
eight 4-ton cars, thus showing a decrease of 281 per cent. 

It will be seen that the grades may be the deter¬ 
mining factor in the number and weight of locomotives 
required, the capacity of the generating station or sub¬ 
station ; also as to the weight of rails, the power demand 
and the power consumption. 

Fig. 12 shows the analysis of a load as observed be¬ 
tween the hours of 7 a.m. and 4 p.m. From the chart 
the plant seems to be as well loaded as is conserva¬ 
tive. It was, however, desired to add to the load 
as shown a hoist demanding 150 kw. at full load, or 


[ 10 ] 















































































































































































































































































































































































an additional 600 amp. In order to determine whether 
the* generating plant could take care of such an addi¬ 
tional demand, a test was run on those loads, which were 
the factors for consideration. 

Figs. 13, 14, 15 and 16 show the demands of the 
locomotive and hoist on different dips. Adding the 
hoist load in this instance simply necessitated prevent¬ 
ing the maximum demands of the locomotives occurring 
simultaneously. Where grades could not be reduced or 
avoided, there were two practical methods available to 
flatten the haulage demand; one, that of a simple signal- 



FIG. 16. POWER CONSUMED BY 2-F LOCOMOTIVES OF 
200-HP., HAULING 14 CARS 

ing device which would indicate trips on grade; the 
other roughly scheduling the main haulage locomotives. 

The majority of mines on careful examination and 
test from an electrical and mechanical standpoint will 
develop the following facts: (1) By systematizing the 
load, a steam station or substation apparently overloaded 
with the breaker tripping many times a day, resulting 
in loss of speed and efficiency, can be operated in a 
normal manner. (2) Conversely, many stations ap¬ 
parently fully loaded can take on more cutting machines 
or locomotives without addition to either substation 
or steam station, as the case may be. 

Table IV, showing a monthly analysis of power con¬ 
sumption, was made with the instruments belonging 
to the mine investigated. The cost of the instruments 
necessary to such an analysis is negligible compared 
with the savings which have resulted from their use. 

It is characteristic of the mine as of the factory that 



FIG. 17. OUTPUT, CONSUMPTION. COST PER TON AND 
PER KILOWATT-HOUR OVER 6 MONTHS 

there is more or less idle machine operation. This is 
particularly true where a mine is equipped with more 
than one converting or generating set. It is, more¬ 
over, generally appreciated that machinery is operating 
at its highest efficiency when approximately fully loaded. 
While the characteristics of power demand in a mine 
make full load operation of most of the equipment out 
of the question, at the same time through analyses such 
as the foregoing, and through systematizing, the power 
consumption and demand of many mines have shown 
marked reduction. This in turn has been reflected to 
a valuable extent on the cost sheet. 

There is a psychological aspect to this as in many 
other cases of economies produced and demonstrated. 



FIG. 18. RATIO OF AVERAGE CONSUMPTION TO FULL 

LOAD CAPACITY 


An organization trained to give thought to such points 
will invariably give thought to other possibilities for 
reducing costs and for increasing the efficiency of oper¬ 
ation. 

Figs. 17, 18 and 19 develop graphically important facts 



Town 

Light Town 
ing Pump 

July. 2,225 528 

August. 1,925 1,548 

September. 2,400 ..... 

October. 2,550 . 

November. 2,750 . 


July. 

August. .. 
September 
October . . 
November 


TABLE IV.—MONTHLY ANALYSIS OF POWER CONSUMPTION 
(Alternating Current Power Consumption, Kilowatt-Hours) 


Sub¬ 










station 

Shop Tipple 

Barn 



A.-C. 

Conver¬ 

M.G.Set 



Light¬ 

Light- Light¬ 

Light¬ 

Shop- Supply 

Rock Car 

Line 

sion 

Effi¬ 

D.-C. 


ing 

ing ing 

ing 

Power House 

Hoist Haul 

Losses 

Losses 

ciency 

Meter 

Total 

31 

10 


260 

530 290 

250 

14,906 

63.0 

25,570 

44,600 

21 

17 


280 

610 280 

250 

16,499 

60.0 

24,670 

46,100 

20 

32 


320 

600 350 

250 

15,068 

64.0 

26,660 

45,700 

5 

27 12 

2 

290 

830 470 

200 

13,694 

70.5 

32,620 

50,700 

8 

60 7 

2 

300 4 

860 450 

200 

14,329 

67.7 

29,430 

48,400 


(Direct Current Power Consumption, Kilowatt-Hours) 






Pneum- 










electric 

Chain 

Mine 

Town Booster Robinson 

Mine 

Stone 

Cutting 



Machines 

Machines 

Pumps 

Pump 

Fans Fan 

Office 

Crusher 

Props 

Haulage 

Total' 

230 

3,180 

9,971 

922 

605 4,192 

3 

560 

. . . 

6,417 

19,153 

202 

4,138 

5,681 

1,219 

490 4,695 

3 

560 

230 

7,454 

24,670 

403 

4,280 

7,020 

1,041 

506 4,800 

3 

... 

... 

8,607 

26,660 

385 

7,216 

7,846 

896 

498 4,718 

5 



10,056 

32,620 

736 

5,904 

7,149 

1,054 

450 4,365 

7 



9,765 

29,430 


[ 11 ] 






























































































































































































concerning the power requirements of a mine. Fig. 17 
gives the tonnage output monthly of the mine investi¬ 
gated through a period of five months. There is shown 
also the monthly kilowatt-hour consumption, the monthly 
cost per kilowatt-hour, the monthly cost per ton and 
the kilowatt-hour consumption per ton. The increased 



FIG. 19. THE IDEAL CONDITIONS OBTAINABLE THROUGH 
USE OF ALTERNATING CURRENT 

■or decreased cost of power corresponding to variation 
of production is also indicated. 

Fig. 18 shows the ratio of the average power con¬ 
sumption to the full load capacity of the substation. 
It shows also the average hourly kilowatt output of 


the station. In addition, the efficiency of the station is 
indicated. This information is provided to correspond 
to the monthly statement shown in Fig. 17. 

It will be observed that the average percentage of 
load—that is, the load factor of this station, which is 
a 200-kw. station—is 19.35 per cent, and that this aver¬ 
age corresponds to the average tonnage of 12,856 tons 
per month. 

Fig. 19 shows the ideal condition that can be obtained 
by using alternating current as far as possible. This 
figure shows the monthly consumption in kilowatt-hours 
of inside fans, pumps and mining machines, both on 
a basis of using alternating-current motors and direct- 
current motors. It is shown that the saving by using 
alternating-current motors would average 7233 kw.-hr. 
per month. 

The foregoing is an excellent illustration of where 
the question is one of applying purchased power, or 
power from a mine power station generating alternating 
current. A large proportion of mines when equipping 
with purchased power continue all of their motor-driven 
apparatus on a direct-current basis. It can be readily 
shown, or in fact deduced from the figures used, that 
where alternating current is available a change-over 
would result in a decreased cost as incident to decreased 
power consumption, as well as demand, which would 
fully justify the change. But most important is the 
desirability of not loading up the substation with a 
load that can be more cheaply and reliably carried by 
stationary transformers. 


r 121 


i 































































Increasing Coal Mine Efficiency—III 

By CHARLES E. STUART 

United States Fuel Administration, Washington, D. C. 


SYNOPSIS — A lack of power capacity is often 
blamed for low voltage at the point of power 
application. This is seldom the root of the diffi¬ 
culty. Increased voltage may often be secured by 
connecting together various existing branches of 
the power line. The mechanical equipment is 
often in extremely bad condition, and a supposed 
shortage of power may be rectified by putting 
engines, boilers and piping in good shape. Elec¬ 
trified mines usually show marked superiority 
over unelectrified ones. 


VI—Analysis of Mine Power Conditions in 
Relationship to Production 

IG. 20 is the resultant of a number of tests at 
different mines and illustrates in excellent manner 
the possibility of improving the voltage of the 
average mine by other means than through the pur¬ 
chase and installation of additional large quantities of 
copper. The improvement as indicated between curve 


3 —I—1—1—1— 
A = Oriainal Losses 

i i i 

in Distribution 







1 

System 

R = I n TV»«vtr*ihi i+inn 








j — 

•after making Improvements with¬ 
out Addition of Feeder Copper 

Z- Losses after making Improve- 
ments including Addition of 
small Amount of Feeder Copper 








o — 








o — 








0 — 

*1 

P 

rupc 

riy 



J 










0 






fi 


- 








0 - 
















0 - 
















0 - 

0 Ls^ 











1 1 

? 1 

2* 1 

A. 1 

R U 


2 3 4 5 6 7 6 9 10 11 12 13 14 15 16 

Distance "from Power* House, Thousand Feet 


FIG. 20. THE POSSIBILITIES OF IMPROVING THE VOLTAGE 
WITHOUT EXCESSIVE ADDITIONS OF COPPER 

A and curve B has been brought about not only by 
taking full advantage of all copper already placed, but 
in addition by improving connections of all kinds. The 
track bonding was perfected. In a word, conditions as 
represented by curve B were as nearly perfect as prac¬ 
ticable without additional copper. 

Between curve B and curve C there is represented 
an improvement resulting from the installation of 
feeder copper. A comparatively small amount of copper 
was necessary to obtain this improvement. That which 
was applied, however, was so placed as to balance the 
system and to place good voltage at points where con¬ 
ditions were most severe, rather than carry the copper 
transmission to those places that are seldom used. 

Fig. 21 represents voltage and amperage readings on 
trips going in and out. The condition of the circuit 
is well indicated. The test deriving this information 
is simple and can be readily run by a capable mine 


electrician with the equipment of instruments which it 
is criminal negligence for any mine to be without. 

The proper application and distribution of copper, 
while not difficult, is a matter for careful consideration, 
analysis and test. Fig. 22 indicates the location and 
capacity of trolley line and feeder copper as well as 
electrical equipment. Analysis of this layout develops 
the following simple measures, of such nature as to 
operate the copper and rail to maximum advantage 
under the conditions existing. 

Referring to this sketch, it would be recommended 
that both 4-0 wires which connect the substation with 
point V should be carefully connected to both trolleys 
going into the mine entrance—that is, both the trolley 
on the empty side and on the loaded side. Points J 
and H should be connected with a 4-0 line; S and V 
should be connected with a 4-0 line; D and T should be 
connected. The following connections should also be 
made: P should be connected with Q. M with N, and 
K with L. 

In some of the foregoing instances the workings will 
have to progress a little farther than they are at 
present, but the advantage of making such connections 
will be readily seen; and it will be apparent that by 
means of these connections the utility of the copper now 
in use throughout the mine will be greatly increased. 

As a general proposition a mine does not take full 
advantage of either its copper or its rail. As a result, 
copper that is unnecessary is frequently purchased. 
Conversely, the motors often operate on a lower voltage 
than is necessary with the copper and rail already 
installed. 

A usual source of power and voltage loss in the 
average mine is at the bonds. Fig. 23 shows a group 
of readings taken at random. The record is a good 
one. The average of a well-bonded track will show a 
bond resistance of 8 ft. of equivalent rail, and 5 ft. is 
regarded as an excellent showing. Higher readings 
may be due to various causes, such as loose terminals 
and the like. Thus, in the placing of bonds the greatest 
care should be exercised in order to see that there is 
no grease or dirt either in the hole or on the bond at 
the time of insertion. Care should be taken that the 
fit be tight. 

Frequently I have found only one side of the track 
bonded. More often there is insufficient cross-bonding 
and almost invariably there are loose terminals. Every 
fifth rail should be cross-bonded. A loose bon^ closely 
approximates a broken connection. Every mine should 
be equipped with a bond-testing device. 

Remember always that the effects of a loose con¬ 
nection, a badly burned switch contact or a grounded 
wire cannot be overcome by increasing the generating 
capacity or the installation of additional feeder copper. 
The parallel of a bad connection is the insertion of a 
section of £-in. pipe in a 2-in. line. Do not simply 
twist a wire connection, but wrap at least 20 turns with 
No. 10 wire and then solder well. Keep all contacts 


[13] 










































of disconnecting switches clean. A corroded or burnt 
switch, or a contact that is imperfect in any way, is 
the equivalent of a loose connection. 

% Extreme low voltage is not necessarily an indication 
that there is insufficient copper. Such low voltage 
may occur in entries where the demand is of infrequent 
occurrence and of short duration. In such cases it 
would readily become a direct waste of money to attempt 
to build up the voltage. On the other hand, at those 
points where the demand is steady, as in the main 
entries, or where there is a steady pumping, fan or 
cutting machine load, the voltage should not be allowed 
to drop below the rated minimum for which the 
machines were purchased and which minimum is stand¬ 
ard with respect to all makes of motors. 

It is the rule where there is frequent armature 
burnout, or in fact where any class of repairs appears 


an actual loss of poWer and corresponding wastage 
of fuel in a greater proportion than the actual voltage 
drop. Second, in a mine where, for instance, there is 
a 25 per cent, voltage drop, and where the station 
appears fully loaded, that this station is actually loaded 
up, not as a result of the work being done, but because, 
practically speaking, all over 65 per cent, of the demand 
represents a direct wastage of energy and a correspond¬ 
ing reduction of capacity. Third, bad power conditions, 
as stated above, mean frequent burnouts and corre¬ 
sponding repair cost. Fourth, there is further entailed 
interruption to service with corresponding reduction in 
output. Fifth, finally, and most important of all, is the 
reduction in the speed and power of the entire equip¬ 
ment of the mine. This may mean that four pumps 
are doing the work that three should do, or that four 
cutting machines are doing the work that should be 



to be too frequently necessary, to blame or disqualify 
the equipment. As a matter of fact, in 99 cases out 
of each 100 the fault does not lie here. Frequent 
burnout or excessive repair costs of any kind, which 
should stand out in a properly developed cost sheet, are 
an indication of neglect of equipment or of equipment 
operated under unfavorable conditions. If a locomotive 
is specified as to weight and motors for the load which 
it is to handle, if the power conditions are approximately 
those under which the locomotive is purchased to oper¬ 
ate, and if the track conditions are reasonably good, 
the repair cost will rarely attract attention. 

But let it be borne in mind that the actual cost 
of repairs represents only a small portion of the total 
cost. The interruptions to service, the loss of time while 
the repair is being made and the demoralization incident 
to the interruptions are the real considerations. 

Bad power conditions mean the following: First, 


performed by three, or that four locomotives are doing 
the work of three; in fact, there has often followed 
an even greater reduction than this in operating effi¬ 
ciency. 

VII—Track Conditions in Relationship to 
Production 

The trackage of a mine and the operating equipment 
in general may be readily compared with that of a 
railroad. In fact a parallel may be drawn at nearly 
every point. It is possible to operate the main haulage 
system on a rough schedule. The method of picking 
up cars is identical. The wrecks and interruptions to 
service arising from badly maintained equipment and 
other mismanagement that have rendered many rail¬ 
roads unprofitable have likewise thrown many mines 
into the hands of receivers and prevented other mines 
from making money. 


[14] 

































































































































The excessive grades, which in the case of a railroad 
cut down train length and necessitate an increase of 
locomotive power beyond reason, have forced identically 
similar burdens on the mine operator. Poor roadbeds 
and badly maintained trackage such as have reduced 
the running time of railroads and rendered their main- 
tenance excessive, find their parallel in the mine. A 
well-laid track, rails of proper weight or if this is 
out of the question at least properly ballasted and 



FIG. 22. DIAGRAM OF THE COPFER CONDUCTOR IN A 

CERTAIN MINE 


properly laid, is one of the best investments that a mine 
owner can make. 

In past years it has been the complaint that many 
of the old Pennsylvania, Ohio and Illinois mines could 
not be profitably operated on account of the long haul. 
The deduction is an incorrect one. There hardly exists 
in this country a mine where the area of development 
is such as would make the haulage system the deter¬ 
mining factor with respect to economical operation. 

A properly laid track kept in good repair means an 
increased production with a decreased cost per ton of 
coal mined. The reasons for this are clear; however, 
they may be stated as follows: There results a speed¬ 
ing up of the entire haulage equipment; decreased 
maintenance cost of locomotives and cars—bumpy track 
causes rapid deterioration of all rolling stock; wrecks 
are practically eliminated; rails not properly ballasted 
or maintained rapidly lose shape not only at the joints, 
but along the entire length. 

VIII—Condition of Generating Plant 

If you generate your own power, what is the con¬ 
dition of your engines and boilers? Will indicating 
engines derive such a curve as that shown in Fig. 24? 
I have observed and helped to make many engine tests 
at mines. Cards such as those shown in Fig. 24 are 
by no means exceptional. 

I recently observed the investigation of a power plant 
of a mine which in most respects is well operated. Seven 
150-hp. boilers were feeding three 200-kw. engine- 
driven generating sets. Using a high-grade fuel five 
firemen were having a hard time maintaining 60 lb. 
of steam pressure. The operator in question proposed 


to purchase additional boilers and generating equip¬ 
ment. Acting on the advice of an engineer, he decided 
not to purchase this equipment but to rebore the engines 
and reset the valves, cover the steam piping and install 
a feedwater heater. The scale was removed from the 
boilers, the tubes thoroughly cleaned and the settings 
repaired. As a result, four of the boilers and two of 
the generating sets carried the load readily. 

This example may appear extreme; but if the man¬ 
ager of the average operation really thinks it is, let 
him conduct a test at his own plant. There is no 
great expense attached to such a trial, and I believe 
that the results in many instances will be amazing. 

IX—Relative Output of Electrified versus 
Unelectrified Mines 

Table V makes a direct comparison between two 
mines operating in the same coal bed, the one electrically 
equipped and the other hand-worked. The table shows 
that the average number of tons produced per day by 
each man is 3.94 in one case and 2.64 in the other. 

TABLE V. COMPARISON BETWEEN AN ELECTRICALLY EQUIPPED 
AND HAND-WORKED MINE 

Electrified Unelectrified 

Thickness of seam. 8 ft. 8 f*t. 

Kind of opening. Shaft Slope 

Method of mining. Machine Pick 

Kind of machines. Electric None 

Method of haulage. Mechanical Mules 

Men employed, total. 402 550 

Miners. 234 305 

Inside men. 108 120 

Outside men. 60 125 

Yearly output in tons. 485,806 450,389 

Output per miner. 2,092 1,476 

Output per man, total. 1,218 819 

Number of days operating308 310 

Numberof tonspermanperday (total) 3.94 2.64 

Number of tons per miner per day 6.79 4.7 

Kind of haulage.{ . 

Thus, there is shown a clear gain of 1.3 tons, or 49 per 
cent., each day by each man in the electrically equipped 
mine. 

Considering the state in which these two mines are 
located and giving due consideration to the character¬ 
istics of the different seams operated, it is estimated 
that if all the mines now hand-worked were to be 



electrically operated, there would be an increase in out¬ 
put of over five million tons; that is to say, the output 
of the state would be increased by over 25 per cent. 

To obtain this increase in output there would be 
necessary an expenditure of about four million dollars, 
or approximately 75c. for each ton of increased yearly 
production. This sum of money in its relationship to 
the value of the increased production and as measured 
by the increased requirements of machinery is relatively 


[15] 


Increase 

Output 

Electrified Mine 
Over 

L’nelectrified 


Per 

Amount Cent. 

616 42 

399 48 

i.'30 50 

2.09 45 










































small when compared with the cost incident to coal 
conservation measures which are under way in many 
sections of the country. 

Table VI shows the cost of cutting coal at a certain 
operation and the estimated cost assuming that elec¬ 
trical equipment were installed. Data gathered since 
a partial electrification has taken place fully bear out 
the figures shown. The table is introduced to show 
the magnitude of the saving made possible through 
the application of the electric drive. 

This table shows that a saving of from 15 to 20c. on 
each ton produced should be possible when the operation 



FIG. 24. A NOT EXCEPTIONAL INDICATOR CARD AND 

POWER CURVE 


is completely electrified. In the state where this oper¬ 
ation is located, assuming a saving of 15c. per ton, and 
with a total production from unelectrified mines of 
11,000,999 tons, the figure of approximately one year 
ago, there would accrue a saving in the cost of produc¬ 
tion in the period of one year of $1,770,000. 

These figures, as stated, represent an analysis made 

TABLE VI. VARIOUS ITEMS IN PRODUCING COAL UNDER PRESENT 
UNELECTRIFIED AND UNDER PROPOSED ELECTRIFIED 

CONDITIONS 


Cost of Cutting Coal Present Proposed 

Labor... 17.00c. 5.70c. 

Power. 4 93 1.12 


Total. 21.93c. 6.82c. 

Cost of Haulage 

Rope. 0.25c. labor 3.30 

Mule. 8.00 power 1.40 

Gas engine. 1.70 hoist 0.20 


Total. 9.95c. 11.72c. 

Cost of ventilation. 0 .49 0.63 

Cost of dewatering. 0.10 0.08 

Cost of screening. 0.19 0.17 

Cost of washing. 0.58 0.27 


Total. 33.24c. 12.87c. 

Cost of Pumping 

River pump. 0.63 0.39 

Cost of operating gin engine larry and tabby. 0.23 0.32 


(Not total, but cost affected by change in power). 34.10c 13.58c. 

Saving. 20.52c. 


in one state. There is, of course, considerable variation 
in costs in this state and with respect to the different 
coal beds operated. Relatively, however, the estimates 
both as to increased production and decreased cost will 
hold true fs between the different beds. They are 
also valuable when considering operating conditions in 
other states. 

The mines that remain unelectrified are numerous. 
In the majority of operations, however, competition 
has forced electrification, even where decreased cost 
and increased production have not proved a sufficient 
incentive. The position of the partially electrified mine 
can be deduced to some extent from the facts given. 



[16] 


















































































Increasing Coal Mine Efficiency—IV 

By CHARLES E. STUART 

United States Fuel Administration, Washington, D. C. 


SYNOPSIS — This article is devoted to the 
efficient electrification of a coal mine using 'pur¬ 
chased power. In many cases, aside from secur¬ 
ing current at a less cost per unit than that for 
which it can he generated, purchasing current has 
the advantage of putting its cost visibly on the 
cost sheet. Care exercised in changing over from 
one source of energy to the other is care well 
spent, as many economies can usually be made. 


W HILE central station power is not available at 
the present time in many coal fields except 
through increasing the demands on stations 
already connected up, there are other coal fields where 
there is a considerable surplus of capacity. In either 
case I believe that the following description will be of 
some value. It may offer suggestions to mines now 
fairly well equipped. It should certainly prove timely 
to operations that are increasing their equipment or 
electrifying new developments. 

Considerably over half of the coal produced today is 
mined with the aid of purchased power. Take the Poca¬ 
hontas fields of West Virginia, for example. The Appa¬ 
lachian Power Co. began to cover this field with its 
transmission system in 1911. Today half of the coal 
of the field is mined with power from this source; an¬ 
other 20 per cent, is mined with power generated in the 
central station of the United States Coal and Coke Co. 



FIG. 25. TYPE OF TRANSFORMER STRUCTURE 
EMPLOYED 



FIG. 26. ROTARY CONVERTER IN UNDERGROUND 
SUBSTATION 


The remaining 30 per cent, is mined with the aid of 
isolated plants, nearly all of which were installed prior 
to the development of the system of the Appalachian 
Power Company. 

The considerations in favor of purchased as against 
manufactured power may be briefly stated as follows: 
The elimination of the supervision necessary to properly 
operate and maintain a power station; elimination of 
skilled and semi-skilled labor, such as engineers and 
firemen, and the conservation of fuel attendant upon 
purchased power. A series of tests in the Pocahontas 
coal field (and these tests represent a pretty fair av¬ 
erage) show that 11.6 lb. of coal are consumed for each 
kilowatt-hour generated. A central station making 
power in that field will operate at about 2i lb. of coal 
per kilowatt-hour. A saving of approximately 9 lb. of 
coal for each kilowatt-hour used, or an average of 9.1 lb. 
of coal for each ton mined is thus possible. 

In the anthracite fields of Pennsylvania, the estimate 
of coal consumed per kilowatt-hour is 16 to 17 lb. In this 
case, and for the purpose of the estimate, steam used 
for fan drive, pumps, etc., has been converted into the 
electrical unit. In fact, it is estimated in the anthracite 
field that a production of 90,000,000 tons of coal repre¬ 
sents at least 9,000,000 tons of coal burned to produce 
power for this tonnage output. Central station elec¬ 
trification of this field would mean a saving of ap¬ 
proximately 8,000,000 tons as now required in the pro¬ 
duction of energy for mining. 

A summary of comparison made in the Pocahontas 
coal field shows 3 kw.-hr. consumed per ton of coal 
produced for purchased power and 5.8 kw.-hr. con¬ 
sumption per ton for manufactured power. This sav¬ 
ing is the result of the elimination of line losses through 
placing the converting stations at the load center, by 
utilizing two-speed fan motors and by the practice of 
economy which invariably follows where the direct rela¬ 
tionship between power consumption and monthly coat 
can be observed. 

With purchased power it is possible to use alternat¬ 
ing current motors for nearly all stationary-motor 


[17] 

















work. These motors are extremely reliable, and they 
require little or no attention except occasional oiling 
of the bearings. They represent the ideal stationary 
motor for the mine, being as nearly foolproof in con¬ 
struction as it is possible to build. As a rule purchased 
power is less costly than manufactured power. This, 
however, is not always the case. There are numerous 
varying factors governing this consideration. 

Before going into a description of a specific installa¬ 
tion it should be stated that it was the intention of the 
mine owner, the engineer and of the power company 
to spare no reasonable expense in order to make this 
installation efficient. I will first give a general de¬ 
scription of the layout of the plant before purchasing 
power, and then show just what methods were adopted 
for the use of purchased energy. 

The main power plant consisted of two 150-kw., 275- 
volt, direct-current General Electric generators direct 
connected to Harrisburg slide valve engines. From the 
main power plant distributing lines were run out at 250 
volts direct current, to supply the mine, fan, tipple, 
pumps, shops, lights and miscellaneous power used. The 
greatest distance from the power plant to the back of 
the lease was approximately 3 miles. This necessitated 
the use of heavy copper extending into the mine 24 
miles. Even then the voltage on the 250-volt circuit 
well back in the mine was as low as 150 volts with 
heavy pulling. 

The fan was located at the drift mouth, 1500 yd. 
from the main power plant and was supplied over a 2/0 
circuit. The voltage delivered at the fan motor was as 
low as 200 when the load was pulling heavy. The fan 
was driven by a 75-kw. Westinghouse direct-current 
generator running as a motor. 

The tipple was driven by ten motors aggregating 
335 hp., varying in size from 75 hp. to 74 hp. and con¬ 
trolled from three different points on different landings. 
As all of this apparatus was operated by one man it was 
necessary for him to go from place to place in starting 
up the tipple and to climb up and down many steps. 
All wiring was of the open type run on knobs and 
through tubes, while in many cases it lay on steel 
girders. Tests were made on each motor separately in 
order to see if any power demand could be eliminated. 
While these tests showed that in several cases machines 
were over-horsepowered, still it was deemed advisable 
on account of the cold weather conditions not to change 



FIG. 27. TRANSFORMERS EMPLOYED UNDERGROUND 



FIG. 28. METHOD OF SUSPENDING ELECTRIC LINE IN 
THE AIR COURSE 

any of the sizes of the motors. The lowest potential 
recorded during this test was 200 volts. The tipple was 
fed by two 4/0 circuits. 

The deep well pump was driven by a 10-hp., 250-volt, 
direct-current motor and was supplied from the circuit 
feeding the tipple, being about 100 ft. therefrom. The 
speed of this motor was varied by means of resistance, 
and in this way it was possible to pump just enough 
water to meet the requirements, without continually 
overflowing the tanks. 

The machine shop was driven by a 10-hp., 250-volt, 
direct-current motor driving line shafting from which 
the various machines such as air compressor, lathe, drill 
press, boring machine and the like, were driven. 

The lights were fed from a three-wire circuit, con¬ 
trolled by three single-pole knife switches, using the 
middle wire as a common return for the two outside 
wires, and maintaining a day and night circuit. Thus, 
by pulling one of the outside switches, the night cir¬ 
cuit could be killed, or, vice versa, the day circuit could 
be switched on. All miscellaneous power such as re¬ 
frigerator, motor for store, general manager’s house, 
meat choppers, etc., were supplied from the day circuit. 

New Equipment for Purchased Power 

I will now give a brief description of the general 
layout adopted. As shown at the beginning, the losses 
were considerable by the time the current reached to the 
most remote point in the mine from the main power 
plant. In order to keep the losses at a minimum, it was 
decided that two substations should be installed, one in 
the existing power plant and one inside the mine. A 
description of each is given separately under “Outside 
Substation” and “Inside Substation,” later on in this 
article. In order to meet the situation most effectively 
it was decided to adopt two different voltages—that is, 
to install two banks of transformers. The type of trans¬ 
former structures used is shown in Fig. 25. In de¬ 
scribing the transformer stations I will designate them 
as bank No. 1 and bank No. 2. 

Bank No. 1 consists of three, lOO-kv.-a. 13,200/440- 
volt transformers located approximately 50 ft. from the 
tipple. From the secondary buses of these transformers 
a three-phase, 440-volt line runs to a main feeder panel 
in the tipple, and three of the two-circuit 4/0 feeder 
wires leading from the main power plant to the tipple 
were converted into a three-phase, 440-volt circuit lead¬ 
ing to the outside substation located in the main power 
plant. The current is measured on the secondary side 
of the transformers, the coal company having a check 


[18] 






















meter installed, as well as a meter on tipple circuit and 
pump, outside substation and lights and shop, thereby 
giving a correct proportion of the power chargeable to 
each installation. 

Bank No. 2 consists of three 75 kv.-a., 13,200/2300- 
volt transformers located at the drift mouth. From 
the secondary buses of these transformers a 2300-volt, 
three-phase line runs into the fanhouse, tapping a three- 
phase bus, from which a circuit is fed through 2300- 
volt disconnecting switches to the fan and through 
2300-volt disconnecting switches and a 2300-volt time¬ 
limit, overload, no-voltage release oil switch to the line 
running to the inside substation. The current is meas¬ 
ured from buses in the fanhouse, the coal company hav¬ 
ing a check meter, as well as a meter on the fan circuit. 

Outside Substation—The outside substation consists 
of a 150-kw., 250-volt, direct-current, six-phase, 1200- 
r.p.m., Westinghouse rotary converter with three single¬ 
phase transformers from 440 to rotary voltage, and a 
switchboard containing all necessary starting and con¬ 
trol apparatus, also one automatic reclosing direct-cur- 
rent circuit breaker, thereby eliminating a constant at¬ 
tendant in the substation. In addition to the direct- 
current feeder for the mine circuit, there is a separate 
direct-current feeder for the larry circuit and boom 
hoist located in the tipple and controlled through cir¬ 
cuit breakers and single-pole knife switches. A direct- 
current meter was installed on the larry circuit showing 
the kilowatt-hour consumption of the larry. 

Description of Inside Substation 

Inside Substation—Before describing the electrical 
apparatus for the inside substation, I should like to give 
a brief description of the location and character of the 
room built to house the necessary apparatus. After hav¬ 
ing selected the space for this substation, which was in 
a breakthrough between air course and main entry, it 
was necessary to remove a considerable amount of coal 
and slate in order to get sufficient space for the in¬ 
stallation. 

The apparatus is installed with a view to being able 
to move any part without interfering with any other. 
For instance, it is possible to move the rotary, switch¬ 
board or any of the transformers without conflicting 
with either of the other two. The walls are built of brick, 
being as thick as the width of a brick on the side walls 
and the length of a brick on end walls. Next to the main 
entry a double door of sufficient size was installed to 
enable removal or replacement of any of the apparatus, 
and a single door opens into the breakthrough leading 
into the air course. By means of ventilators located in 
both doors, it is possible to regulate the amount of air 
flowing, and in this way the substation is kept cool at 
all times. From the roof the slate was taken down as 
far as the sandstone top, and left in this condition. 
This has thus far given satisfaction, and from all ap¬ 
pearances will continue to do so. 

The apparatus for this substation consists of a 150- 
kw., 250-volt, direct-current, six-phase, 1200-r.p.m., Gen¬ 
eral Electric rotary converter, with three single-phase 
transformers stepping the voltage down from 2300 to 
rotary voltage, and a switchboard containing all neces¬ 
sary starting and control apparatus, also one automatic 
reclosing direct-current circuit breaker. The inside sub¬ 
station apparatus is shown in Figs. 26 and 27. 


When it was decided to install this substation in the 
mine, estimates were made in order to ascertain if it 
would be more feasible to put a borehole down through 
the mountain or run a line through the air course. It 
was finally decided to adopt the latter. Accordingly a 
three-phase, 2300-volt line was constructed and run 
through the air course. The type of construction is 
shown in Fig. 28. Some anxiety was felt as to how this 
line would hold up on account of slate falls, but a care¬ 
ful inspection of the air course was made and all loose 
slate or any that was thought likely to fall was taken 
down. 

This line has been in operation now practically a year 
and there have been only two interruptions; and these 
were not of a serious nature. The oil switch located in 
the fanhouse kicked out, but when closed again the line 
showed clear. It is therefore believed that small pieces 
of slate fell, causing a momentary short-circuit. The 



FIG. 29. OIL AND DISCONNECTING SWITCHES IN THE 

FAN HOUSE 

oil switch located in the fanhouse, with disconnecting 
switches and other apparatus, is shown in Fig. 29. 

In place of the 75-kw. generator operating the fan a 
100-hp., two-speed, 2300-volt Allis-Chalmers induction 
motor was installed together with a starting compen¬ 
sator, pole-changing switch, and two sets of overload 
and no voltage releases, these being of the two-coil type, 
one to operate on high speed and one to operate on low 
speed, thereby guaranteeing safety from overloads on 
both operations. As stated before, there is a separate 
meter on the fan circuit showing the exact kilowatt- 
hours chargeable to ventilation. 

Special attention is called to the method of control 
adopted for the tipple. This is shown in Fig. 30. The 
operator, a one-armed man, has all of his control appa¬ 
ratus located at one central point and arranged so that 
he can start each machine in its proper order. All wires 
for the tipple motors were figured and installed of suffi¬ 
cient capacity so that the total drop from the second¬ 
ary buses of the transformers to the motor would not 
exceed 5 per cent. All wiring was run in conduit with 
proper condulets installed on each outlet. Practically all 
motors were of the slip-ring type, thereby taking care of 
the heavy starting load, which was a source of nuisance 
with the direct-current motors, especially in cold 
weather. 


[19] 


/ 




















A 10-hp., 440-volt, two-speed induction motor was in¬ 
stalled to handle the pump load, thereby enabling a two- 
speed operation in order to meet the condition, as de¬ 
sired, for this service. A separate meter was installed 
on this circuit in order to obtain the amount of power 
chargeable to water supply. A 10-hp., 440-volt induc¬ 
tion motor was installed in the shop, driving line shaft¬ 
ing to which all operating machines were connected. 

The three-wire, 250-volt, direct-current circuit was 
converted into a three-phase. 440-volt circuit, the two 
outside legs of this circuit being controlled through cir¬ 
cuit breakers and the middle leg through a single-pole 
knife switch. From this three-phase circuit leading out 
of the substation 440/110-volt transformers were in¬ 
stalled to take care of the lighting and miscellaneous 
power. These transformers were so located that no sec¬ 
ondary lines from the transformers would exceed 500 
ft. in length using No. 8 wire for secondaries. There 
are two single-phase meters installed back of the switch¬ 
board on the three-phase, 440-volt circuit for measur¬ 
ing the kilowatt-hours chargeable to lights aud miscel¬ 
laneous power. 

The accompanying figures for purchased power are 
based on actual records up to June of 1918. The fig¬ 
ures for manufactured power are based on 1914 records, 
allowing for the increase of costs, as incident to present 
conditions. These figures show a reduction in power 
cost; also, a reduction in kilowatt-hours consumed. The 
mine fan, due to the delay in arrival of certain control 
parts, has never been operated at half speed. 

Certain special considerations incident to the applica¬ 
tion of purchased power arise and require determina¬ 
tion. Among these is the question of selection of motor- 
generator set or rotary converter. Within the last 
five or six years the 60-cycle rotary converter has been 
brought to a state of construction perfection where it 
is one of the most satisfactory and reliable pieces of 



FIG. 30. GROUPED CONTROL APPARATUS IN THE TIPPLE 


conversion equipment that can be obtained. This is 
true whether the case in question is one of operating a 
single-unit substation, the parallel operation of units 
in the same substation, or of parallel operation of two or 
more substations located at different points. 

The rotary converter will carry a remarkably heavy 
overload without flashing. In fact it will readily carry 
from 100 to 200 per cent, overload on peaks of short 
duration such as are characteristic of the mine load. 


Moreover, the operating efficiency is much greater than 
that of the motor-generator set. Difference in efficiency 
becomes more pronounced when considered with respect 
to the low load factor which is characteristic of the mine 
load. Fig. 31 is designed to compare the efficiency of 
a 200-kw. motor-generator set with that of a 200-kw. 
rotary and of a 150-kw. rotary. This particular com- 



FIG. 31. COMPARATIVE EFFICIENCIES OF TWO ROTARIES 
AND MOTOR GENERATOR 

parison was made for a mine which was using a motor- 
generator set, but increasing its substation capacity. 

Based on the monthly output of the motor-generator 
set over a period of five months, it was determined 
that by the installation of a rotary converter and 
assuming a power cost of lc. per kw.-hr., the 200-kw. 
rotary, if substituted, would save $628 per year. The 
changeover was made in the case referred to, although 
the motor-generator set had at the time been in opera- 


MANUFACTURED POWER (COST) 


Power Consumption, 859,209 Kw.-Hr. 

Coal 2761 tons @ $2.40. 

Engine repairs.. 

Generator repairs. 

Boiler repairs. 

Sundry tools. 

Supplies from store. 

Cost for ash disposal.. 

Fire insurance and workmen’s compensation 

Firemen and engineers. 

Repairs—labor. 


Tons Mined, 215,457 

. $6,526.40 

. 807.00 

. 36.34 

. 530.00 

. 79.74 

. 58.10 

. 109.32 

. 420.20 

. 5,047.00 

. 518.29 


Total. $14,457.3* 

Superintendence. 2,000.00 

Depreciation. 844.12 


Total. $17,301.51 

Cost per kw.-hr.... $0.02013 

Kw.-nr. per ton mined. • 4 

Cost per ton mined. $0. 08052 

PURCHASED POWER (COST) 

Tons mined. 233,460 

Purchased power (822,660 kw.-hr.). $9,876. 00 

Repairs to substations. 196.56 

Supplies from store. 19.92 

Substation attendant. 282.00 

Fire insurance and workmen’s compensation. 125.28 

Superintendence. 2,160. 00 

Depreciation. 844.08 


Total. $13,503.84 

Cost per kw.-hr. $0. 01641 

Kw.-nr. per ton mined. 2.84 

Cost per ton mined. $0.05660 


tion through a period of about two years only. The re¬ 
sults have been as anticipated. 

Rotaries of the same rating as the motor-generator 
sets replaced have shown themselves to be of relatively 
greater capacity. Likewise they have shown equally 
as great reliability in service. I do not recommend 
the rotary under all circumstances; however, where the 
system from which the supply of power is obtained is a 
modern one, there is little or no exception. 


[20] 
























































Increasing Coal Mine Efficiency—Y 

By CHARLES E. STUART 

United States Fuel Administration, Washington, D. C. 


SYNOPSIS — This, the last article of the 
series on this subject, deals with central sta¬ 
tion conditions and problems. Many such stations 
are overloaded during the day, and as additional 
equipment is difficult to obtain these stations 
and their war-industry customers are faced with 
some objectionable but not altogether destructive 
alternatives. 


I N MANY mine centers served by central stations, as 
well as in other war-industry centers such as the 
Pittsburgh and Philadelphia districts, there is a 
growing power shortage and in other sections an ap¬ 
proaching shortage. This fact is due to the rapidly 
increasing demand incident to the speeding up of in¬ 
dustry to meet war necessity. I am familiar with a 
case where the demand on a central station serving coal 
mines almost exclusively has doubled within the period 
of a year. 

Fig. 32 is a load curve of one of the largest central 
stations in the country serving mines. It will be ob¬ 
served that the demand is actually in excess of the 
present capacity of the generating station. In this 
particular case the present condition is the result of 
breakdowns. At the same time the company in question 
has insufficient reserve capacity and for that reason the 
failure of one of its larger units is sufficient to curtail 
service to the entire system. 

Additional Units Mean Increased Investment 

The question will be asked: Why not increase the 
generating capacity by additional units? To do this, 
as a rule, involves heavy investment cost. Many of the 
utility companies under present operating conditions 
cannot show a balance that would enable them to finance 
such an investment. Moreover, where satisfactory earn¬ 
ings are shown, there arises the question incident to 
the present high cost of apparatus and the relationship 
of such excessive cost to the conditions that will exist 
after the war, and particularly when the load falls off. 

But even where the financial condition of a company 
is favorable, as is true in cases, there is involved the 
impossibility of financing against Government require¬ 
ments and the difficulty of financing under the rules of 
the War Finance Corporation. 

In spite of these considerations, the central stations 
are obtaining a great deal of financial assistance where 
it is necessary. However, even with funds needed for 
improvement in hand, equipment must be obtained and 
installed under nearly impossible conditions. There is 
a demand for turbine equipment far in excess of the 
supply. A turbine of any size today cannot be obtained 
within a year. Boiler manufacturers are in the same 
condition as are the turbine builders. 

Where a breakdown occurs there is delay in effecting 
repairs, even with all the priority assistance that can 
be given. Furthermore, there is the consideration of 


skilled labor necessary to look after the complicated 
requirements of a central station system. Linemen and 
other similar help are not exempted. The chief en¬ 
gineer or the chief dispatcher in the central station is 
liable to call on short notice, with attending demoraliza¬ 
tion to service. All of these facts are focusing the 
consideration of the mine owners and central station 
operators toward establishment of measures of relief. 

Mine Power Service Receives Priority 

In Pittsburgh and Philadelphia recently the office 
hours of buildings, department stores, lofts and other 
similar power users have been staggered. No lighting 
or elevator service, for instance, is allowed to meet such 
requirements between 7:30 a. m. and 10 a. m. Mine 
power service in the Pittsburgh district has been given 
priority over service to all other war industries; thus, 
the steel mills in the Pittsburgh district are being sub¬ 
jected to shutdowns, while the coal mines are kept 
running. Non-war loads, such, for instance, as the glass 
manufacturers, have been required to go on night shift. 
Certain war loads are doing the same. The steel mills 
are already operating a night shift. 

There are a number of alternatives with which the 
coal operators, as well as the central stations serving 
mines, will be faced, as conditions grow more acute. 
Some of these are enumerated as follows: Placing all 
non-war loads on night shift, insofar as they conflict 
with the mining or other war-industry loads. Placing 
cutting machines and pumps on night shift, where this 
particular class of load, if so placed, would take sufficient 
demand from the day load to be of assistance. This is 
now being done in the West Virginia fields. To stagger 
the loads—that is to say, start certain mines at an 
early hour in the morning, other mines a few hours later, 
and so on, thus flattening out the peak, and where condi¬ 
tions are extreme, to operate groups of mines on alter¬ 
nate days. The advantages from such procedure would 
be that the mines in operation would have continuous 
service and would not be subject to frequent shutdowns 
throughout the day, which has been found to be far 
more disastrous to the output than the alternatives 
suggested. 

Staggered System in West Virginia 

The precedent for these suggestions was the arrange¬ 
ment made in the West Virginia coal fields a few months 
ago when a large unit broke down. In that case certain 
mines were operated in the morning and other mines 
in the afternoon. 

The West Penn Power Co., of Pittsburgh, is suffering 
at the present time through a lack of capacity. In this 
case all non-war load has been thrown on night service. 
Even so, however, the demand is still in excess of the 
capacity by about 10 per cent. It has been arranged to 
cut off certain circuits for a period not exceeding 10 
minutes and to rotate the cutoff so as to include all of 
the mines during the day. Thus, any one mine is liable 
to cutoff from one to three times per day for a period 


[ 21 ] 




\ 


of 10 minutes at each cutoff, or a total of 30 minutes 
during the day. 

The result of the foregoing is to more or less sys¬ 
tematize interruptions. The mines know when an in¬ 
terruption occurs that it is not going to last for more 
than 10 minutes. It is not possible to give any previous 
notice of an interruption, since the circuits are only 
taken off as the demand on the power plant exceeds a 
certain capacity, and that demand can never be predicted 
in advance. In this connection it has been found neces¬ 
sary to arrange for better cooperation between the tele¬ 
phone company, the central station and the mine, so that 
information concerning interruptions can be quickly 
transmitted. 

There remains the radical alternative of night opera¬ 
tion of mines. At the present time the West Penn 
Power Co. is taking on no new contracts unless the min- 


There are, however, bn account of established prece¬ 
dent in this country, many difficulties to be overcome, 
and it is with a full knowledge of these difficulties, both 
physical and psychological, that I suggest that night 
operation may become inevitable in certain centers. 

Not to do an injustice, it may be observed that many 
of the central stations serving mines have today ample 
capacity for their present as well as for additional load. 
Moreover, it is difficult to say that an operator with his 
own plant, the demand upon which is increasing, is in 
a particularly favorable position. The difficulty of ex¬ 
panding individual installations or of making new ones 
involve the same element of time, and the same con¬ 
siderations of high cost and skilled labor as those per¬ 
taining to central stations. 

Today it will be far simpler from all angles to meet 
any large demand for additional power by increasing 



ing company is willing to operate at night. By referring 
to Fig. 32 it will be seen that after four o’clock in the 
afternoon and before seven in the morning the load 
curve is far within the generating capacity. Between 
these hours it is possible to take on additional load. 

A few mines have accepted the alternative of operat¬ 
ing at night, but they have not been on this service 
long enough to report results. However, it can be readily 
seen that the adoption of such an alternative may be¬ 
come inevitable, if production is to be maintained. 
Though the suggestion where made has been received 
with considerable disapproval, it may be noted that 
already many classes of war industries are accepting 
the inconvenience attendant upon night operation. 

It is difficult to see why, if the steel mills, for instance, 
in normal times can satisfactorily operate on night 
shift, the mines cannot do the same, provided the neces¬ 
sity is sufficiently urgent. England, France and Ger¬ 
many in peace times have all established the precedent of 
a night shift. In a number of the mining centers of 
this country cutting machines and pumps have always 
been operated at night. 


central station capacity than by the expansion of isolated 
plants, or the building of new isolated stations. Finally, 
it should be observed that through following some of 
the prescriptions elsewhere indicated, the operator him¬ 
self can go a long way toward assisting the central 
station to take care of its load. 


[ 22 ] 
















































































































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